| NZR P class (1885) | |
|---|---|
| Power type | Steam |
| Builder | Nasmyth, Wilson & Co. |
| Serial number | 272–281 |
| Build date | 1885 |
| Total produced | 10 |
| Configuration | 2-8-0 |
| UIC classification | 1′C n2G |
| Gauge | 3 ft 6 in (1,067 mm) |
| Driver diameter | 41 in (1,041 mm) |
| Length | 50 ft 6 1⁄2 in (15.41 m) |
| Weight on drivers | 27.7 long tons (28.1 t) |
| Locomotive weight | 32.5 long tons (33.0 t) |
| Tender weight | 20 long tons (20 t) |
| Fuel type | Coal |
| Fuel capacity | 2.2 long tons (2.2 t) |
| Water capacity | 1,300 imp gal (5,900 l; 1,600 US gal) |
| Boiler pressure | 135 psi (0.93 MPa) |
| Firegrate area | 15.8 sq ft (1.47 m2) |
| Heating surface: Total |
858 sq ft (79.7 m2) |
| Superheater type | None |
| Cylinders | Two, outside |
| Cylinder size | 15 × 20 in (0 × 1 m) |
| Top speed | 20 mph (32 km/h) |
| Tractive effort | 11,415 lbf (50.78 kN) |
| Career | New Zealand Railways |
| Locale | Otago, Auckland |
| Disposition | Withdrawn |
The P class was a class of steam locomotives built to haul freight trains on the national rail network of New Zealand. The class consisted of ten individual locomotives ordered from the British company of Nasmyth, Wilson and Company in 1885, but miscommunications about the weight limitations imposed on the locomotives meant they did not start work until 1887. This debacle came at a time when the New Zealand Railways Department (NZR) was suffering from a lack of motive power to work on its rapidly expanding network and was part of what prompted a shift towards American and home-grown manufacturers.
The classification of this class as "P" was the first example of the re-use of a classification that had previously been used for an earlier class. The members of the P class of 1876 had been sold to private companies or the Public Works Department, leaving the classification unused. The Railways Department chose to assign it to this class, setting a pattern that was followed with other classes in years to come, with the most prominent example being the A class of 1906 re-using the classification of the A class of 1873.
Initially, seven of the P class locomotives were deployed in Otago, with the remaining three based in Auckland, and in 1899, the Auckland fleet expanded to four when one was transferred north from Otago. The locomotives started their lives with wooden cabs in a Gothic style, but they were later replaced with steel cabs. The V class was the equivalent of the P class for passenger train duties, and recorded examples exist of overhauls where a member of one class was re-boilered with the boiler from an engine of the other class.
By 1926, all four Auckland members of the P class had been withdrawn from service, and the six southern members were retired within the next four years. Multiple members of the class are known to have been dumped in rivers to provide riverbank stability and halt erosion, and two of these (P 25 and P 107) were recovered from the Clutha River in 1992 by Project Steam of Dunedin. Roughly a decade later, another two members of the P class (P 60 and P 133) were recovered from the Oreti River near the Wairio Branch and are in the possession of the Ohai Railway Board Heritage Trust. The goal of both organisations is to restore at least one of their engines to full operational condition, following in the footsteps of the restoration of K 88 at the Plains Vintage Railway, and it is believed some considerable progress has been achieved on rebuilding P 107.